Chris Kings have much better bearings and the drive ring design is objectively stronger. Hydras are lighter and don't require any proprietary tools to work on (except for the drive ring). I've had 3 pairs of Hydras, one pair of Torches and never owned Chris Kings. I've shredded one I9 drive ring which was replaced under warranty (the Hydra drive rings are not serviceable by anyone other than I9). Kings are stronger yet heavier, with better bearings. I9s are lighter, easier to work on and even though they just use basic Enduro bearings, bearings are cheap, easy to replace and don't require adjustment unlike the angular contact bearings Chris King uses